Genetic Dissection of Drought Resistance and Drought Escape QTLs in Durum × Wild Emmer Wheat RIL Population Through Relationship to Phenology

Drought is the major abiotic stress limiting wheat productivity, affecting more than 40% of wheat growing areas. Breeding high-yielding drought-resistant cultivars is considered a sustainable approach to increase crop productivity. We used a recombinant inbred line (RIL) population derived from a cross of Triticum durum (var. Langdon) X Triticum dicoccoides (acc. G18-16) previously evaluated under water-limited and well-watered conditions for mapping quantitative trait loci (QTL) of 19 traits. In order to discriminate between 'true drought tolerance' and 'drought escape', we used regression analysis to adjust the phenotypic data by time of flowering. The resulted QTLs were classified into four groups: (i) QTLs obtained after analysis of the initial data set without adjustment (iQTL); (ii) QTLs obtained after adjustment for time of flowering (dfQTLs); (iii) QTLs reflecting drought escape (dQTLs); and (iv) QTLs reflecting 'true drought tolerance' (ddfQTLs). A total of 150 iQTLs were identified based on non-adjusted data, and additional 36, 102 and 33 dQTLs, dfQTLs and ddfQTLs, respectively. These QTLs were co-located in 80 loci: 54 loci classified as independent of flowering time, five loci were classified as drought escape and 27 as drought tolerance loci. The obtained results indicate that regression analysis can be used as a simple and effective method to reduce the bias caused by variation in flowering time in detection of drought related QTLs, as well as in addressing other similar problems in genetic dissection of stress tolerance.